panasonic tc-l32c22 Making hum sound and wont power up

[reelitin]

I have a panasonic tc-l32c22, I went to turn it on last week and it makes a sound like a cd placed in a laptop tray but not clicked in. I took the back off, turned it on again and have found the piece that is making the noise.
I am new to repairing tv's and discovered this forum trying to see if i could find a solution.
I have included a picture of the board and the piece I suspect to be the issue. My question is if I need to replace the whole board or if I can replace the piece that is the culprit.
Any help is greatly appreciated.
Jason

[ben7]

Re: panasonic tc-l32c22 Making hum sound and wont power up

The transformer should not make a humming noise, if it does make any noise, it should be a high pitched whine. My guess is one of the mains filter caps is bad

[electronicsurplus]

Re: panasonic tc-l32c22 Making hum sound and wont power up

I am dealing with the same exact television. If you search the model # you will find the posting and the answers there may help you also as to how to check it. Do you have any voltages on pins of the connector from the PS to the main board? if so what are the voltages?

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Thanks, I will check the voltages in the am-have a fathers day picnic today- and will post back what i find.
thanks for the support and wealth of knowledge
Jason

[tom66]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Does it sound like "chig-a-chig-a-chig-a" several times a second? Bad startup cap or shorted diode on secondary.

[electronicsurplus]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Tom, Any ideas yet on this television? I bought yet another Power supply and, still has the same problem which means it must be the main board. Any idea where I should look?

I have sent you a service manual with schematic for this set as well as others

Jon

[tom66]

Re: panasonic tc-l32c22 Making hum sound and wont power up

I've not dealt with any Panasonic LCDs, so my advice is limited. I'd suggest it's not on the PSU if you've replaced it; probably the A board or similar.

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Sorry for the delay in responding to everyone-this site is great. I had some things come up and the tv got put on the back burner.
When I do turn it on it does make a whining sound on the item that i have circled in previous picture. Then the red power light will blink twice pause for a second and blink twice again.
I am new to working on tv's but within one week I lost 2 tv and now am thinking i can possibly fix it rather than purchasing a new one. I have been reading all over this site to try and learn without asking dumb questions but any help would be apprectiated.
thanks
jason

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Sorry it has taken so long to get back to this issue. I have a couple questions in regards to taking readings of the pins. what do i put my ground pin of my meter to? and secondly someone mentioned that it sounds like "Bad startup cap or shorted diode on secondary." Is there a way to look and see they are bad, a way to test this, etc. None of the capacitors appear to look abnnormal, but sometimes i know they dont completely bulge out or look burned.
I appreciate the help from this site as I do not have the funds to take it to a shop to get fixed.
Jason

[tom66]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Do you have a digital multimeter? Can you take a high resolution shot of the PSU board?

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Yes I have a meter - a fluke, dont know the exact model.
I hope these pics are good enough, was having trouble with lighting. If you need different please let me know.
Thanks again for your help
Jason

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

The board I took 2 pics of is the board that is making the noise when turned on. Didnt know if this is the board you were talking about and that was the reason I took of both.

[budm]

Re: panasonic tc-l32c22 Making hum sound and wont power up

OK, I look at the service manual, the transformer that is making noise T7301, it generates the 32V for backlights inverter circuit, 12V, and 17V.
It may be in the shutdown mode.
Please check the DC voltage on C7214 (120uf 450VDC), it should be about 400VDC.
Then check the resistance reading of the 4 MOSFET's in the inverter drive circuit: Q7801, 7802, 7803, 7804 with Ohm mode.
Take the reading like this:
Pin1 & 2
Pin 1 & 3
Pin 2 & 3.

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Hello
Sorry it has taken so long to get back in regards to this matter and I truly appreciate the knowledge that is so graciously given on this site.
I took the board off that you asked so that I could check the C7214 and I discovered a burn spot on the back of the board and matching on the panel it mounts to. It lines up directly with where the power plugs in coming from the other board.
I have attached pics and hopefully this will help. I didnt do any further checks of what you asked as I thought this might have a big reason to the issue at hand. Although I am very mechanically inclined, and I have built and installed numerous car stereo systems- so i feel I have somewhat of an idea of how to follow instructions and learn a new set of skills. I will apologize in advance if I ask a question that I should know.

[budm]

Re: panasonic tc-l32c22 Making hum sound and wont power up

The pictures are way out off focus to tell what that section is for in the circuit.

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

Sorry I used my phone and then used PAINT to draw the arrows which must have distorted them.
I took these in sunlight with a pen pointing at the burn spot on the board and the other side where it lines up at.
Thanks for looking and helping

[budm]

Re: panasonic tc-l32c22 Making hum sound and wont power up

That is the incoming AC Neutral pin, if it arced like that, that mean there was a some kind of conducttive material beteen that Neutral pin and the chassis ground. The thing that bother me is that the Neutral wire of your house wiring is tied to safety ground at the breaker panel so there should be close to 0VAC between Ground and Neutral pin to cause the arcing like that unless you outlet wiring has HOT and Neutral reversed. You should get one of those AC outlet polarity checker to find out.
But any way, that is at the AC input to the board, so as long as the the Two AC input pins see 120VAC at the that white connector, it should be OK. So we still have the problem some where on the board.

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

It was in a house built in 1921 and that room had not been rewired but was on a surge protector. It did happen in a storm, but the surge protector did not trip and it is a quality surge protector. I will check the voltage and we will work from there.
thanks again for all your help

[reelitin]

Re: panasonic tc-l32c22 Making hum sound and wont power up

I checked and they are reading 122.5. So that is not the issue.
When I check the DC voltage of C2714 and I am not getting a reading above a volt. I did this by plugging in the power plug onto the board and checking the solder points on the board. Is this the correct method?
Appears to me that this may be the issue. Would I be on the right track?

[budm]

Re: panasonic tc-l32c22 Making hum sound and wont power up

You mean C7214 Main filter cap as in post #13? It should have about 165VDC when TV is plugged in and about 400VDC when TV is turn on. Make sure to use black lead of the meter connected to the Negative leg of C7214 which is the Primary side ground point.